This invention relates to ionization chamber, x-ray detectors. More specifically, this invention relates to multi-cellular x-ray detectors which comprise two-dimensional arrays of high pressure ion chambers for use in computerized tomography systems.
In computerized x-ray tomography a spatial distribution of x-ray intensity must be translated into electrical signals which are processed to yield image information. Detectors for use in such systems must efficiently detect x-ray, electromagnetic energy with a high degree of spatial resolution. The information rate in tomography systems is generally limited by the recovery time of the x-ray detectors. It is desirable, therefore, to utilize x-ray detectors characterized by fast recovery times, high sensitivity, and fine spatial resolution. Proposed tomography systems employ arrays of hundreds of such x-ray detectors. A multicellular construction, wherein multiple, spatially separated x-ray detection cells are incorporated in a single assembly, provides an economic means for the production of such systems.
Arrays of ionization chambers are typically used to measure the distribution of intensity in computerized transverse axial tomography equipment. In a typical application of such equipment, a moving x-ray source is repeatedly pulsed to transmit x-ray energy along a plurality of distinct coplanar ray paths which pass through a body undergoing examination. Energy transmitted through the body is detected in an ionization chamber array and interpreted, by the use of a digital computer, to produce cross-sectional images of the internal body structures in the plane of examination. A typical tomographic diagnostic procedure involves the production of images in a series of closely spaced, substantially parallel planes passing through a region of the body. Successive scans may be accomplished by translating either the patient or the x-ray equipment along an axis passing through the body. A three-dimensional reconstruction of internal body structures may, thus, be determined from the set of images produced.
The rate of production of tomographic images in such systems is necessarily limited by the time required to accomplish the physical rotation and translation of the mechanism. Typically, one second or more is required to accumulate the data necessary to produce an image in a single plane. Reconstructions of large body regions will, therefore, often be confused by movement of the patient, or of his internal body organs, during the course of an examination procedure.